There are many reasons for believing high chloride {100} tabular grain emulsions, the invention of Maskasky U.S. Pat. Nos. 5,264,337 and 5,292,632, to be ideal for a variety of photographic applications. Tabular grain emulsions are well known to offer improved sharpness and an improved speed-granularity relationship. Silver chloride emulsions are recognized to be ecologically attractive and to possess the capability of rapid processing. Silver chloride grains with predominantly {100} crystal faces are recognized to have a high degree of shape stability, allowing morphologically stable {100} tabular grains to be formed.
Recently interest in precipitating high chloride {100} tabular grain emulsions has been directed to processes that can be analyzed as containing a step that creates grain nuclei containing crystal lattice dislocations that promote the growth of high chloride {100} tabular grains and a subsequent step in which the grain nuclei are grown into {100} tabular grains. The following patents are representative: House et al U.S. Pat. No. 5,320,938; Chang et al U.S. Pat. Nos. 5,413,904 and 5,663,041; Yamashita et al U.S. Pat. No. 5,641,620; and Oyamada et al U.S. Pat. No. 5,665,530.
All of the above patents employ a gelatino-peptizer. It is generally understood that gelatin used to form the gelatino-peptizer is derived from the collagen of warm blooded animals. The majority of gelatin employed in preparing silver halide grain containing photographic elements is derived from the bones and, to a lesser extent, the hides of cattle. Acid-treated gelatin, such as pig-skin gelatin, is also employed. These common origins of photographic gelatin are acknowledged in Research Disclosure, Vol 389, September 1996, Item 38957, II. Vehicles, vehicle extenders, vehicle-like addenda and vehicle related addenda, A. Gelatin and hydrophilic colloid peptizers, paragraph (1) and explained in detail in Mees, The Theory of the Photographic Process, Revised Ed., Macmillan, N.Y., Chapter 3, The Preparation and Properties of Gelatin, pp. 48-98.
It has been recognized that gelatin derived from fish skin can be employed as a peptizer in the preparation of the silver halide emulsions, as illustrated by Mori et al Kokai 95/287334, published Oct. 31, 1995, filed Apr. 15, 1994. Band, Photographic Gelatin, Royal Photographic Society, London (1987), pp. 17-22, contains a section by R. E. Norland, titled, "Fish Gelatin, Technical Aspects and Applications".